You said: "better now than later", especially while there's no kids?"
I say - YES! I'm so sorry you are going through this, but really, you need to recognize that it is a GOOD thing you don't have kids with this woman. - She's weak (who gets married just because they got proposed to in a public place and didn't have to guts to tell you they were having second thoughts?). - She's selfish (SHE blows up the marriage but YOU are the one couch surfing while SHE sleeps in your home???) - She's dishonest (don't believe for a moment that she went to her sister's to think it over and just had a random hookup with some guy - I place my bets on her having a boyfriend). - She's unkind
Are these the qualities you want in the mother of your children? Is this the person who will have your back when the chips are down?
She's telling you who she is.
My ex told me who he was, too, when he slept with an old girlfriend the night before our marriage. I worked to patch it up, and went on to make a family with him. I patched it up again when he cheated on me when our kids were in their early teens. Then when he left several years later, I realized what an idiot I had been - he'd shown me that this was who he was all along! Unfortunately my kids paid the price for my stupidity and are suffering as a result of their parents divorce after 24 years.
A sitch like yours is one where I say move on. I know it is shocking and difficult, but just work on being a better you and try to figure out how you missed this side of her personality, so you will choose better next time.